The present invention is directed to a process of heating parts in a double band press for transferring heat to the material being processed in the press. In addition, the invention is directed to a device for carrying out the process including a heating device which heats the heat transfer medium and is connected over a supply line and a return line to opposite ends of medium flow passageways through the press parts.
It is known from German Offenlegungsschrift No. 24 21 296 to utilize double band presses for fabricating continuous, sheet-like materials, in particular for the production of decorative laminates, chipboards, fiberboards, electrolaminates or the like. Such presses include two press bands each stretched over a pair of reversing drums with the material being processed passing between the press bands where pressure and heat are applied so that the material is hardened. The heat required in the pressing operation is passed from the reversing drum located at the press inlet and the drum is heated by a heat transfer medium with the heat passing into the material being processed. In addition to the reversing drums, additional parts of the double band presses are heated by the heat transfer medium so that the entire press stand is maintained at a uniform temperature. It has been found that local temperature differences in the press stand can result in differential thermal expansion and such expansion can have a deleterious effect on the final dimensions of the finished product being processed in the press. It is also necessary to assure that there are no temperature differences in the heated reversing drums, since such a situation would result in temperature differences being transmitted through the press bands to the pressed product.